March 25, 2014

Perovskite Holds Promise For Inexpensive Solar Cells That Light Up At Night

Today, when your mobile phone or tablet runs out of power, you have to let it recharge for hours plugged into a wall socket. A new study from the Nanyang Technological University (NTU) demonstrates that, in the future, all you might need to do it put it out in the sun.

The NTU research team has developed a next-generation solar cell material that converts light to electricity, as well as being also able to emit light. The base for the solar cell is Perovskite, a promising material that could hold the key to creating high-efficiency inexpensive solar cells, which not only glow when electricity passes through, but can be customized to emit different colors.

For example, the outer facade of a shopping mall could store solar energy during the day, and transform into a light display for advertisements that glow after dark.

The discovery that Perovskite could emit light was made almost by chance. The team leader, NTU Assistant Professor of physics Sum Tze Chien, asked his postdoctoral researcher, Xing Guichuan, to shine a laser on the new hybrid solar cell material.

To their surprise, the solar cell material glowed brightly when the laser was shone on it. Most solar cell materials are good at absorbing light, making the discovery of one that generates light rather significant. Not only is the new, highly luminescent, material able to emit light but it is very good for making lasers as well.

“What we have discovered is that because it is a high quality material, and very durable under light exposure, it can capture light particles and convert them to electricity, or vice versa,” said Asst Prof Sum, a Singaporean scientist at NTU’s School of Physical and Mathematical Sciences (SPMS).

“By tuning the composition of the material, we can make it emit a wide range of colors, which also makes it suitable as a light emitting device, such as flat screen displays.”

Sum worked with Assistant Professor Nripan Matthews from the School of Materials Science and Engineering (MSE) and the Energy Research Institute @ NTU ([email protected]). Matthews said that this newly discovered property is expected to enable the industry to adopt the new material for use in existing technology.

"What we have now is a solar cell material that can be made semi-translucent. It can be used as tinted glass to replace current windows, yet it is able to generate electricity from sunlight."

“The fact that it can also emit light makes it useful as light decorations or displays for the facades of shopping malls and offices,” said Dr Matthews, who is also the Singapore R&D Director of the Singapore-Berkeley Research Initiative for Sustainable Energy (SinBeRISE) NRF CREATE program.

“Such a versatile yet low-cost material would be a boon for green buildings. Since we are already working on the scaling up of these materials for large-scale solar cells, it is pretty straightforward to modify the procedures to fabricate light emitting devices as well. More significantly, the ability of this material to lase, has implications for on-chip electronic devices that source, detect and control light,” he added.

Experts are already praising the new solar cell material. “This work from the NTU SinBeRISE team clearly shows the promise of such new materials in a broad range of applications, including solar cells and now for lasing. It also shows the power of interdisciplinary, basic science in making fundamental discoveries that will impact in a broad sense," said Professor Ramamoorthy Ramesh, the Purnendu Chatterjee Endowed Chair in Energy Technologies professor at the University of California, Berkeley. Ramesh has over two decades of experience leading world-class research in the areas of electronics and solar materials.

The team detailed the inner workings of the solar cell material in the Science journal last October. The material is currently patent pending, but is estimated to be five times cheaper than silicon-based solar cell due to its easy solution-based manufacturing process. This process works by combining two or more chemicals at room temperature.